The present invention relates to an apparatus for determining concentrations of mineral elements contained in an alloy. Particularly, the present invention relates to an apparatus for determining concentrations of mineral elements, which is suitable for an analysis of an alloy containing a small amount of mineral elements.
Conventional apparatus for determining concentrations of mineral elements, as shown in FIG. 1 comprises a glow discharge lamp (GDL) 10 adapted to atomize ,elements ,consisting a sample S to be determined and excite the atomized elements so as to emit a light L, a spectrometer 20 adapted to diffract said light L emitted from said GDL 1 into various angles and detect the strength of said diffracted lights, a vacuum maintaining device and argon gas-supply system 30 adapted to maintain the interior of the GDL 0 under the vacuum condition and supply argon gas to said interior of the GDL 10, a high voltage supply 40 adapted to apply a high voltage to the GDL 10, an A/D converter and amplifier 50 adapted to amplify the electric signal from the spectrometer 20 and convert it into a digital signal, and a computer 60 adapted to treat said digital signal from said A/D converter and amplifier 50, calcuate the composition and the strength of elements consisting said sample S, and control the concentration-determining apparatus.
The inner space 11 of the GDL 10 is sealed by the sample S and a first window 12. An anode 13 and a cathode 14 to which the high voltage is applied are provided in the GDL 10. The sample S is connected to the cathode 14, so as to function as a cathode. The spectrometer 20 comprises a casing 21 an a second window 22 arranged at a certain part of said casing 21. Through the second window 22, the light L emitted from the GDL 10 passes. In the interior of the casing 21, the spectrometer 20 also includes a focusing lens 23 adapted to focus the light, a grating 24 adapted to diffract said focused light L, a slit plate 27 having an inlet slit 25 positioned at the path of an incident light and a plurality of outlet slits 26 through which said diffracted light from said grating 24, pass and photo multiplier tubes (PM tubes) 28 adapted to determine the strength of the diffracted light which have passed through said outlet slits 26 of the slit plate 27. The outlet slits and the PM tubes 28 are arranged at the path through which among the diffracted lights from the grating 24, several lights of certain wavelengths pass.
Now, the operation of the conventional apparatus for determining concentration of mineral elements will be described in detail.
First, a reference alloy sample S, in which the concentrations of the elements consisting the alloy are known, is attached on the GDL 10, as shown in FIG. 1. By the high voltage supply 40 and the vacuum-maintaining device and argon supply system 30 controlled by the computer 60, the interior of the GDL 10 is maintained under a proper vacuum condition of, for example, about 10-10.sup.-1 Torr, and argon gas is then injected into the interior of the GDL 10. As the high voltage supply 40 applies the high voltage to the interior of the GDL 10, an electric field is established between the anode 13 and the cathode 14. The electric field causes the argon gas to acceleratively flow toward the reference sample S and impact thereupon, so that some atoms of the elements consisting the reference sample S are separated. The atoms of the separated element impact against the electrons formed between two electrodes and the argon gas. In process of this impact, the atoms of the elements absorb an energy and is excited from a ground condition to a high energy the excited states. The excited atoms return from the excited state to the ground state, emitting a light corresponding to the resonance frequency of atoms. This process is continued while the voltage is supplied. Accordingly, the resonance of all elements consisting the reference sample S is discharged from the GDL 10, The discharged light L comes into the spectrometer 20, via the first window 12 attached to the GDL 10 and the second window 22 attached to the spectrometer 20. Thereafter, the light L passes through the focusing lens 23 and the inlet slit 25. Then, the light L is focused on the grating 24. The focused light is diffracted into various angles according to the wavelength. The strength of each light diffracted by the grating 24 is determined by each PM tube 28 which is arranged in the path of light passing through an outlet slit 26.
If the reference sample S contains three elements to be measured, the light L discharged from GDL 10 is mixed with the frequencies F.sub.1, F.sub.2, and F.sub.3 of said elements. This light L is diffracted into three angles by the grating 24 disposed in the spectrometer 20. The three diffracted lights pass through the outlet slits 26, respectively. The three PM tubes determine strengths of the lights which have frequencies F.sub.1, F.sub.2, and F.sub.3, respectively.
Thereafter, the strengths I.sub.1, I.sub.2, and I.sub.3 of the lights determined by the PM tubes 28 are amplified and converted into digital signals by the A/D converter and amplifier 50. The digital signal is memorized in the computer 60. The strengths I.sub.1, I.sub.2, and I.sub.3 memorized in the computer 60 correspond to the known concentrations C.sub.1 C.sub.2, and C.sub.3 of elements, respectively.
After the determination is completed, with regard to the reference sample S, an alloy which contains the same kind of the elements as those of the reference sample, but of unknown concentrations is substituted for the reference sample. As the alloy is treated in the above-mentioned manner relating to the reference sample S, the strengths I.sup.'.sub.1, I.sup.'.sub.2, and I.sup.'.sub.3 corresponding to the respective unknown concentrations C.sup.'.sub.1, C.sup.'.sub.2, and C.sup.'.sub.3 of three elements of the alloy can be received by the computer 60. The computer 60 compares the strengths I.sup.'.sub.1, I.sup.'.sub.2, and I.sup.'.sub.3 with the strengths I.sub.1, I.sub.2, and I.sub.3 and calculates values the respective concentrations C.sup.'.sub.1, C.sup.'.sub.2, and C.sup.'.sub.3 by a software equipped in the computer 60. Thus, the concentrations of the elements to be determined can be found.
However, when several kinds of mineral elements have to be simultaneously analyzed by using the above-mentioned conventional apparatus, the apparatus needs a plurality of expensive PM tubes 28, the number of which corresponds to that of the elements to be measured. This results in the increase of the manufacturing cost. Additionally, it is necessary to provide a complex high voltage circuit and safety device, so as to actuate a plurality of PM tubes 28. In order to increase the resolution of the diffracted lights from the grating 24, the PM tubes 28 are arranged at the position remote from the grating 24, thereby causing the spectrometer 20 to have a large size.